Radiolucent zone of the patella following total knee arthroplasty without patellar resurfacing

Background

The radiolucent zones in the patella are sometimes observed in patients who have undergone total knee arthroplasty (TKA) without patellar resurfacing. On the basis of radiological findings from our clinical experience, we hypothesize that the pathogenesis of this lesion may be similar to that of the lesions of spontaneous osteonecrosis, and this lesion may be due to both osteoporosis and stress concentration. The present study aimed to determine the incidence of the radiolucent zone after TKA without patellar resurfacing. Moreover, the roles of osteoporosis and patellar morphology, which are related to the stress distribution in the patella, were also investigated.

Methods

We studied 48 knees of 38 patients who underwent primary TKA using the Genesis II prosthesis. Axial radiographs taken 1 year postoperatively were used to assess the incidence of the radiolucent zone. The World Health Organization fracture risk assessment tool (FRAX) score and the preoperative patellar facet angle were compared between patients with and without the radiolucent zones.

Results

Five patellae (10.4 %) showed the radiolucent zones postoperatively (the radiolucent group), whereas no such lesions were found in the remaining 43 patellae (the normal group). The major osteoporotic fracture risk of the radiolucent group calculated using the FRAX was 24.8 % and significantly higher than that in the normal group (14.7 %; p = 0.01). The average patellar facet angle in the radiolucent group was 123.6°, which was significantly smaller than that in the normal group (133.6°; p = 0.003).

Discussion and conclusions

The results of the present study suggest that both underlying osteoporosis and a steep patellar facet angle may play an important role in the pathogenesis of the radiolucent zones in patellae after TKA without patellar resurfacing. Patellar resurfacing may be considered, particularly in osteoporotic patients who have a steep patellar facet angle, to avoid the appearance of the postoperative radiolucent zone in the patella.     

The patellofemoral joint after total knee arthroplasty without patellar resurfacing

One hundred total knee replacements with a total condylar prosthesis and without patellar resurfacing were followed for a minimum of two years. Eighty-four per cent of the knees were affected by osteoarthrosis. Graded according to the knee-rating system of the Hospital for Special Surgery, there were eighteen excellent, fifty-three good, eighteen fair, and eleven poor results. At the most recent follow-up, twenty-nine knees (29 per cent), nine of which were affected by rheumatoid arthritis, were still painful in the patellofemoral area. The height and weight of the patient definitely influenced the amount of patellofemoral pain postoperatively. Small patients who had osteoarthrosis were exceptionally free of pain, regardless of sex, age, or level of activity. It seems that the best approach to patellofemoral replacement includes resurfacing of the patella in all patients who have rheumatoid arthritis and in patients who have osteoarthrosis if they have preoperative patellofemoral pain, are more than 160 centimeters tall, weigh more than sixty kilograms, and have advanced changes in the patella at the time of the operation.     

Total knee arthroplasty without patellar resurfacing

One hundred and eleven total knee replacements without patellar resurfacing were followed-up for a minimum of 48.8 months (range 48.8-108.2 months; average 78.2 months). Evaluation was performed using the Knee Society Clinical Rating System (KS-CRS). Preoperatively, the mean knee score was 34.3 points and the mean function score was 42.2 points. Postoperatively, this knee score improved to a mean of 91.1 points and the function score improved to mean of 89.6 points at the most recent follow-up. There were no significant differences among the knees with mild, moderate, or severe degenerative change to the patella with regard to the preoperative (p=0.83) and postoperative (p=0.39) knee pain score. It seems likely that the postoperative knee pain is not related to the severity of degenerative change to the patella in total knee arthroplasties performed without patellar resurfacing, and none of those patients required patellar resurfacing to achieve knee pain relief.     

Total knee arthroplasty without patellar resurfacing

Twenty-seven knees treated between 1974 and 1980 had a total condylar type knee arthroplasty without patellar resurfacing; the average follow-up period was 5.2 years. Compared with a previously reported group of 100 consecutive total condylar arthroplasties, the overall results in this series were very similar. However, there was a significant difference in stair-climbing ability, and one-third of the patients could not use the operated knee for this activity. In most knees the patella could be resurfaced. A working hypothesis assumes that the patellar button can be omitted in patients with relatively normal patellar cartilage, or relatively young, active, or obese patients who are considered a high risk for patellar bone fractures.     

Patellar clunk syndrome in total knee arthroplasty without patellar resurfacing

In a series of 647 total knee arthroplasties, the patella was not resurfaced if bony geometry of the patella was good enough to maintain good congruency of the patella undersurface to the femoral component and the patella was tracking normally at the femoral component groove at the time of surgery. Three hundred seventy-two total knee arthroplasties were done with a femoral component that had the same geometry as the original total condylar prosthesis. None of these knees resulted in patellar catching, whether the patella was resurfaced or not. Two hundred seventy-five total knee arthroplasties were done with a more contemporary femoral component with wider intercondylar space and shorter posterior extension of the intercondylar notch. Eleven of these 275 knees demonstrated catching of the patella at 60° to 90° of flexion when the knee was tested from flexion to extension during the surgery. All of these 11 knees did not have patellar resurfacing during surgery at first. Of these 11 knees with patellar catching noted during surgery, at first, patellar catching was eliminated with patellar resurfacing in 4 and by shaving of the superior pole of the patella in 7. None of the knees with the patella resurfacing in this series showed patellar catching.     

Technique for patellar resurfacing in total knee arthroplasty

The proper size of the patellar component for a total knee arthroplasty can be determined with the use of a caliper. The thickness of the patella is measured prior to removing the articular surface and again after the trial component has been inserted into the patella. The measurements should be approximately the same in thickness. It is important to select the proper patellar component to avoid loss of flexion of the knee, a very prominent patella, and postoperative subluxation of the patella.     

The role of patellar resurfacing in total knee arthroplasty

The ideal treatment of the patella in primary total knee arthroplasty (TKA) for osteoarthritis (OA) remains unclear. Although data exist in the literature to support either resurfacing or not resurfacing the patella, evidence continues to emerge that unresurfaced patellas deteriorate with time. Recent prospective, randomized studies also favor patellar resurfacing over retaining the native patella, reporting reoperation rates to convert unresurfaced to resurfaced patellas exceeding those for complications after patellar resurfacing. In addition, the incidence of residual patellofemoral pain after secondary resurfacing is substantially higher than when patellofemoral resurfacing is done primarily. Patient selection criteria are critical in the decision-making process. Patellofemoral complications, the greatest argument against resurfacing, have been diminished with improved surgical techniques and implant design.     

髌骨周围电灼去神经化对保留髌骨的全膝关节置换术膝前痛的Meta分析

目的 以Meta分析方法研究髌骨周围电灼去神经化对保留髌骨的全膝关节置换术（TKA）膝前痛和膝关节功能的影响.方法 检索关于保留髌骨行髌骨周围电灼去神经化TKA的相关文献,按照特定的纳入和排除标准筛选文献并提取相关数据,用Review Manager 5.0软件进行Meta 分析.结果共纳入四篇随机对照研究.分析表明髌骨周围电灼去神经化对保留髌骨的TKA患者术后膝前痛的发生率无影响[RR=0.76,95%CI （0.59,1.00）,P=0.05],但是可以改善其的Feller髌骨评分[MD=1.15,95%CI （0.74,1.55）,P〈0.01],KSS评分系统-膝关节评分[MD=1.30,95%CI （0.23,2.37）,P〈0.05]和KSS评分系统-膝关节功能评分[MD=1.45,95%CI （0.08,2.81）,P〈0.05].结论 在保留髌骨的全膝关节置换术中使用髌骨边缘电灼去神经化能改善术后膝前痛和膝关节功能.     

Advantages of patellar resurfacing in total knee arthroplasty

Complications of patellar resurfacing in total knee arthroplasty have rekindled the interest of many surgeons in patellar retention. In a prospective study 20 randomly selected patients of 40 underwent patellar resurfacing in combination with their total knee arthroplasty. The other 20 patients were left with an unresurfaced patella. Within 24 months of follow-up, the advantages of patellar resurfacing could be seen according to the Knee Society Score. Especially in advanced osteoarthritis of the knee joint, the patients achieved better scores in climbing stairs and in function. The superior functional results are arguments for patellar resurfacing, at least in knees with advanced osteoarthritis.     

Retropatellar contact characteristics in total knee arthroplasty with and without patellar resurfacing

Total knee replacement with and without patellar resurfacing was performed in 6 cadaver specimens. The contact pressure and contact area between femur and patella was measured at 60° of flexion. In comparison to specimens without resurfacing the specimens with small size resurfacing showed a significant decrease in contact area, whereas average and maximum pressure were unchanged. In specimens with medium size resurfacing, contact area and average pressure increased slightly, whereas maximum pressure increased significantly. Patellar resurfacing did not change the retropatellar pressure, but was associated with reduced contact area.

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Résumé  6 cadavres ont été examinés après implantation d’une prothèse totale du genou avec et sans implants de restructuration de la surface rotulienne. Les mesures de la pression et de la surface de contact ont été réalisées avec une flexion du genou à un angle de 60°. En comparant les résultats de genoux sans implants et genoux avec implants de la rotule de taille ”petite”, on remarque que ces derniers ont causé une diminution significative de la surface de contact rétro-rotulienne. Les pressions moyenne et maximum n’ont pas changé de manière déterminante. Les implants de taille ”moyenne” ont conduit à une augmentation considérable de la pression maximum et à une diminution significative de la force alors que la surface de contact et la pression moyenne ont elles, légèrement augmenté. Après la pose des deux types d’implants de la rotule on a constatée une réduction significative de la surface de contact, mais ne pas de la pression rétro-rotulienne.

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Accepted: 24 January 2000     

Systematic review of patellar resurfacing in total knee arthroplasty

Controversies existing over resurfacing the patella in total knee arthroplasty remain in the literature. The purpose of this review was to evaluate the effectiveness of resurfacing versus nonresurfacing the patella in total knee arthroplasty. We searched the Cochrane Library, MEDLINE and EMBASE for published randomised clinical trials relevant to patellar resurfacing. The relative risk of reoperation was significantly lower for the patellar resurfacing group than for the nonresurfacing group (relative risk 0.57, 95% confidence interval 0.38–0.84, P = 0.004). The overall incidence of postoperative anterior knee pain of the 1,421 knees included was 12.9% in the patellar resurfacing group and 24.1% in the nonresurfacing group. The existing evidence indicates that patellar resurfacing can reduce the risk of reoperation with no improvement in postoperative knee function or patient satisfaction over total knee arthroplasty without patellar resurfacing. Whether it can decrease the incidence of anterior knee pain remains uncertain.     

髌骨钻孔减压改善全膝关节置换术后膝前疼痛

目的探讨通过髌骨钻孔减压术改善全膝关节置换术(TKA)后膝前痛的临床疗效。方法将符合标准的113例行TKA的骨关节炎患者按数字法随机分为两组:54例为减压组,TKA术中联合髌骨钻孔减压术;59例为非减压组,仅施行TKA不联合髌骨钻孔减压术。术后观察两组患者切口愈合情况、相关并发症、KSS评分及膝前痛发生率。结果两组患者切口均一期愈合,无严重并发症发生,113例均获满12个月的完整随访。KSS评分:减压组术后明显高于非减压组;术后膝前痛的发生率明显低于非减压组,差异均有统计学意义(P0.05)。结论 TKA术中联合髌骨减压术可以在一定程度上改善膝关节KSS评分及降低术后膝前疼痛的发生率。     

Patellar contact forces with and without patellar resurfacing in total knee arthroplasty.

Patellar contact forces were measured in 7 fresh-frozen cadaver knees during continuous flexion-extension cycling for the normal knee and after total knee arthroplasty without and with patellar resurfacing using 2 prosthesis systems with different designs for the femoral and patellar components. Analysis of variance with specimen as a repeated measure was used to examine the effect of contact surface. When compared to normal knees, total knee arthroplasty without patellar resurfacing resulted in no change in patellar contact forces. The magnitude of the inferosuperior patellar shear force increased significantly after patellar replacement with an oval, biconcave patellar component and increased further after replacement with an oval, domed patellar component. There were no significant changes in the mediolateral and anteroposterior contact force components after patellar replacement.     

全膝关节置换术中髌骨置换与否对膝前痛发生的影响

[目的]回顾性分析、比较全膝关节置换术中髌骨置换与否对膝前痛发生的影响,为临床治疗提供参考。[方法]对1994年10月~2004年10月行人工全膝关节置换术病人125例(148膝)按髌骨置换(84膝)和未置换(64膝)分为2组,并对其随访资料进行分析,膝关节评分采用HSS评分系统,髌骨评分采用Feller评分标准。结果使用SPSS统计软件进行统计学分析。[结果]置换组HSS评分由术前的(39.6±39.8)分进步为末次随访时的(90.9±8.2)分,髌骨评分由(14.4±6.4)分进步到(25.2±4.8)分,膝前痛分数也由(4.6±3.9)分进步为(10.6±4.1)分;未置换组HSS评分由术前的(38.8±9.8)分进步为(90.2±8.9)分,髌骨评分由(14.2±6.2)分进步到(25.1±4.8)分,膝前痛分数也由(4.8±3.8)分进步为(10.3±4.1)分。2组患者末次随访时膝前痛均较术前明显减轻,差异有显著性意义;置换组与未置换组比较,膝前痛减轻的差别无显著性意义。[结论]无论髌骨置换与否,患者的合理选择和正确的手术操作是避免术后膝前痛的关键所在。     

Novel customized template designing for patellar resurfacing in total knee arthroplasty

Due to the irregular shape of patella and difficulty in identifying its bony landmarks, it can be a challenge for surgeons to accurately and symmetrically perform patellar resurfacing. Three‐dimensional (3D) models of 20 patellae were generated from computed tomographic images. Using a computer‐assisted preoperative planning technique, customized template designs were developed to guide patellar resurfacing. The patellar models and corresponding templates were produced through rapid prototyping. The accuracy of this technique was assessed after applying the templates on patellar models and cadaver specimens, respectively. Using preoperative planning and predesigned templates, a significant improvement in symmetric patellar resurfacing, with a mean angle of 1.21° mediolateral (ML) obliquity and 1.95° superoinferior (SI) obliquity, was observed compared with the conventional sawguide technique (mean angle of ML and SI was 4.13°, 4.95°, respectively). Additionally, the use of customized templates reproduced the desired preplanned patellar resection. Preoperative planning with 3D imaging and customized templates improved the accuracy of patellar resurfacing in terms of the obliquity and thickness. Clinical Relevance: A novel customized template designed for patellar resectioning will benefit surgeons in performing patellar resurfacing. This technique will provide accurate patellar resurfacing in clinical practice. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1798–1803, 2016.     

The outcome of three methods of patellar resurfacing in total knee arthroplasty

Summary Two hundred and three patients with 219 Miller Galante type I knee arthroplasties have been reviewed in a multicentre study at an average of 3.5 years after operation. Three groups are compared: 83 patients were treated with a full polyethylene patellar component; 68 with a metal backed component, and 68 with patellar debridement without resurfacing. We found no differences between the 3 groups in relation to pain, range of movement, stability, flexion or extension deficit, extension lag, alignment, walking distance, ability to climb stairs or the use of walking aids. There was also no difference in the incidence of patellofemoral complications. The number of revision operations was the same in patellar-resurfaced and non-resurfaced knees. Lateral release was accompanied by more complications in every subgroup.

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Résumé Dans un travail multicentrique nous avons étudié 219 arthroplasties de Miller Galante type 1 chez 203 patients avec un suivi postopératoire de 3.5 ans en moyenne (de 2 à 6). On a comparé trois modes de traitement: 83 fois un implant rotulien en polyéthylène, 68 fois une plaque métallique postérieure, les 68 autres malades furent traités par débridement simple sans revêtement artificiel de la surface articulaire. On n'a trouvé aucune différence entre les trois groupes quant à la douleur, la mobilité, la stabilité, le déficit de flexion ou d'extension, l'impossibilité d'extension active, l'alignement, la distance de marche, la montée des escaliers ou la nécessité d'utiliser des cannes. En outre le taux de complications patello-fémorales était le même pour les trois groupes. Le nombre de réinterventions ne différait pas selon que les malades avaient bénéficié ou non d'un recouvrement de la face postérieure de la rotule. C'est la section de l'aileron externe de la rotule qui a entraîné le plus de complications dans les trois groupes.

     

Evidence in orthopaedics: patellar resurfacing in total knee arthroplasty

Abstract Four good quality randomized clinical trials comparing patellar resurfacing versus noresurfacing in knee arthroplasty are analyzed. The outcomes evaluated were anterior knee pain, scores on the Knee Societys rating system and reoperation.No relevant differences were found in knee scores, but anterior knee pain was less frequent in patients with patellar resurfacing. Few patients had severe anterior knee pain. Still, patients with anterior knee pain were less satisfied with the clinical result. Studies with longer follow-up showed that anterior knee pain increased with time in both groups. A clinically relevant increase in reoperation rate in the nonresurfaced group could not be excluded with the numbers available.Anterior knee pain seems to be influenced by the decision of resurfacing the patella during knee arthoplasty. Although it is not associated with important changes in knee scores, patients perceive it as a cause of insatisfaction. Influence of patellar resurfacing on implant supervivence is not clear.